Diesel cars are less reliable and more expensive to fix than their petrol counterparts, according to a study by MotorEasy.

It analysed repairs of 30,000 three to eight year old cars over a 12-month period and found diesel models broke down three times more, on average.

Drivers of diesel models were also hit with bigger repair bills. The average engine repair bill for a diesel was £517, compared with £433 for a petrol model, a difference of 20%.

Duncan McClure Fisher, founder of MotorEasy, said: “Diesels experience many more small problems than petrol cars. They are less reliable and, when a big item goes wrong, it costs a lot more to put right."

He advised: “If you’re still considering a used diesel car, our advice is to avoid high-mileage examples, particularly if you are only driving low mileage or doing city driving.”

Engine faults were found to be far more prevalent in diesels than petrol cars, the biggest repair cost found by MotorEasy amounted to £4,030.80.

Of the brands studied, Alfa Romeo, Land Rover, Kia and Mazda diesels have the highest average diesel engine repair cost versus petrol counterparts.

Least reliable diesel cars by make

Make	Average diesel failure rate
Alfa Romeo	47%
Land Rover	41%
Mitsubishi	36%
Saab	33%
Mazda	33%
Kia	29%
Mercedes	27%
Vauxhall	26%
Mini	26%
Audi	26%